A 2-year-old girl presented with progressive hyperpigmentation of both the distal interphalangeal joints of fingers and toes along with palmar and plantar hyperpigmentation of both hands and feet for the last one year with no other associated symptoms. Clinically, her weight (13.5 kg), height (91 cm) and developmental assessment were appropriate for age. Her other systemic examination but for her skin pigmentation were all normal. Investigations were not contributory, other then a low vitamin B12 level (84.2 pg/mL) and mild megaloblastic picture in bone marrow. A diagnosis of Imerslund-Grasbeck syndrome (IGS) was considered and was treated with intramuscular injection of 1000 µg methylcobalamin daily for 7 days, followed by weekly injections for 1 month and then oral doses of 1000 µg daily. With therapy, there was a significant change in 10 days time and there was total resolution of skin lesion in a month’s time. She was advised to have lifelong daily therapy with 1000 µg oral methylcobalamin.

Hyperpigmentation due to vitamin B12 deficiency appears only in patients whose skin is normally pigmented, hence may not be a feature in Caucasians, whereas it is more common in darker-skinned patients. In Indian children, isolated mucocutaneous lesions could be one of the earliest signs of B12 deficiency [1] that may predate other systemic manifestations. IGS should be considered in any individual with macrocytic anemia, reduced serum B12 levels and proteinuria. This child with IGS had only skin manifestation on presentation, probably with time haematological manifestations could have surfaced, as evidenced by the marrow revealing megaloblastic changes despite other haematological indices being normal. Life-long treatment with vitamin B12 is necessary for IGS, which alleviates hematologic, gastrointestinal and CNS symptoms except proteinuria [2]. High oral doses of B12 (1000 µg and 2000 µg) is safe, acceptable and as effective as intramuscular administration [3,4]. Oral treatment is based on the finding that in larger doses, sufficient amounts are absorbed even in the absence of intrinsic factor.

Available literature suggests that, pigmentary changes remain unresponsive with vitamin B12 replacement in IGS as was observed in two Chinese siblings [5]. This child with vitamin B12 replacement had complete resolution of skin pigmentation but her proteinuria persisted even on follow up for 3 years.

To conclude, a diagnosis of vitamin B12 deficiency has to be considered in any case of isolated skin hyperpigmentation.